One point to keep in mind as we watch the results tonight. A lot will depend on whether the race has now shaped up with both Clinton and Obama and roughly-matched and known contenders, or whether, because of her history and name recognition, Clinton is the de facto incumbent vs. Obama the challenger. It could make a very, very big difference because a number of the polls we’re seeing have high undecideds. And it is a very reliable rule of thumb that undecideds break for the challenger.
The thinking behind that rule of thumb is that the undecided voter knows the incumbent. And if they haven’t decided to vote for them by election day they’re very unlikely to do so. In other words, the late undecided voter in most cases is a voter who’s decided to vote against the incumbent but hasn’t quite gotten their head around the idea yet.
It’s a pretty reliable rule. But is she the incumbent? The one example I can think of that points against that is New Hampshire. My recollection is that Obama’s final numbers were pretty close to what the polls predicted. The ‘surprise’ was that the undecided broke overwhelmingly for Clinton, thus giving her her margin of victory. South Carolina seemed to point in the opposite direction.
